According to a conventional door lock, the engagement of the lock latch in the latch channel at the jamb is a straight locking and unlocking, i.e., the flat-plate latch is horizontally driven into a " "-shaped latch channel to maintain the door in locking condition. For unlocking the door, the latch will be pulled out of the latch channel in the reverse and straight motion.
The aforesaid method can be rather easily sabotaged by a door picker. The latch of the conventional lock with one locking step has only a short portion extending into a latch channel, and the lock of that type can be unlocked easily by a door picker by hitting the door with such a force so as to move the door body and the deform latch, and then the latch will be pulled out of the latch channel, as can be seen very often in the movies.
Further, in the conventional two-step or three-step locks, the latch can be deeper introduced into the latch channel than that of the one-step type of lock, but the depth of the latch channel is still limited by the thickness of the door jamb. To sabotage a two or three-step type of lock, the door picker usually inserts a crowbar between the door body and the jamb to cause a gap (in order to facilitate the door to open and close, a gap is usually maintained between the door body and the jamb) and so as to retract the latch a given length; then, the door picker or burglar pushes or hits the door with force to have the latch retracted out of the latch channel, and the door will be opened in unauthorized manner.
Briefly, in the conventional locks, no matter whether an electronic lock or mechanical lock, usually a straight type of latch engage in linear motion or straightly into the latch channel; and, therefore, it is very easy for the door picker to pry the door open with a crowbar.
In view of the aforesaid disadvantages of the conventional door locks, the inventor has, through repeated studies and improvements, developed a substantially sabotage-proof lock comprising an elbow-shaped latch. The latch of the lock is substantially secured against being pried out, and it can substantially prevent a door with my type of lock from being forcefully and unauthorized opened by a door picker or burglar.
The lock device according to the present invention includes a transmission mechanism, which can drive respective upper and lower latches to slide along an elbow-shaped groove. The latches are first driven to slide horizontally to enter into the latch channel in the jamb, and then driven to slide vertically until entering into the latch sockets respectively. After the L-shaped latches are engaged with the walls of the latch sockets, it will be very difficult to pry the latches out with a crowbar.